Matos signed with the San Francisco Giants as an international free agent in July 2018 for a signing bonus of $725,000.[8][9][10] He spent his first professional season in 2019 at 17 years of age with the Dominican Summer League Giants and Rookie-level Arizona League Giants, batting a combined .367/.438/.566 with 65 runs, seven home runs, 48 RBIs, and 21 stolen bases in 24 attempts in 251 at bats over 60 games.[11] In the Dominican Summer League (DSL) he led the league with 24 doubles and batted .362(8th in the league)/.430/.570(9th) in 234 at bats with 60 runs (3rd), seven home runs (7th), 47 RBIs (3rd), and 12 hit by pitch (3rd).[12] He was a DSL mid-season All Star, a DSL post-season All Star, and a Baseball America DSL All Star.[13]
Matos did not play a minor league game in 2020 due to the cancellation of the minor league season caused by the COVID-19 pandemic. He played the 2021 season with the Low-A San Jose Giants, as one of the youngest players in the league.[14][15][16] Over 109 games, he led the California League with 84 runs, 86 RBIs, 35 doubles, 21 stolen bases, and five sacrifice flies and slashed .313(7th in the league)/.359/.495(9th) in 451 at bats with 15 home runs (2nd), 28 walks (5th), and seven hit by pitch (3rd).[17] He was the California League Most Valuable Player, a California League post-season All Star, and an MiLB Organization All Star.[13]
In 2022, playing for the Rookie-level Arizona League Giants (for only seven at bats) and High–A Eugene Emeralds in the minor leagues, Matos batted an aggregate .215/.280/.356 in 376 at bats with 58 runs, 12 home runs, and 47 RBIs, while dealing with an injured quadriceps.[5][18] With the Emeralds, he had the lowest strikeout rate among qualified hitters in the league.[14] He then played for the Scottsdale Scorpions in the Arizona Fall League, batted .233/.280/.361 in 86 at bats, and was named Arizona Fall League Defensive Player of the Year.[13] He was ranked # 2 in the Giants 2022 MLB Prospect Rankings.[19] On November 15, 2022, the Giants added Matos to their 40-man roster to protect him from the Rule 5 draft.[20]
Matos began the 2023 season with the Double–A Richmond Flying Squirrels, and batted .304/.399/.444 in 115 at bats.[21] He was then promoted to the Triple–A Sacramento River Cats, where he was 5.7 years younger than his fellow Pacific Coast League ballplayers, and batted .398(leading the league)/.435/.685(4th) in 108 at bats with six steals in seven attempts, before he was called up on June 14, 2023, for his major league debut.[21][22][18] At 21 years of age, he was the youngest player in Triple–A.[23]
He was promoted after left fielder Mitch Haniger suffered fractured forearm in the previous night's game, and Matos was slotted in the lineup as the starting center fielder against the St. Louis Cardinals.[24] On June 14, 2023, Matos batted second and went 1-for-3 with a run scored in his MLB debut.[23] At 21 years of age, he became the second-youngest position player in MLB; only Cardinals outfielder Jordan Walker was younger. [14] In 76 games during his rookie campaign, he batted .250/.319/.342 with two home runs and 14 RBI.
Matos was optioned to Triple–A Sacramento to begin the 2024 season.[25] After being called up in mid-May, he drove in 17 runs in his first six starts, thus becoming the first Giant awarded National League Player of the Week since Brandon Belt in 2018.[26]